The lighting industry is quickly changing from fluorescent and incandescent light bulbs to a more efficient method, such as light emitting diodes (LEDs) to light the world's commercial and residential segments. Current light emitting diode (LED) technologies, such as LED light bulbs, LED strip lighting, and LED modules operate on direct current (DC), and thus require a transformer or other converter to convert typical AC (alternating current) mains power into the DC (direct current) required to power the diodes. As LED technology is adopted, many fixtures which currently operate with old light sources, such as incandescent and fluorescent bulbs, are being replaced with LEDs. AC mains voltage is typically 120 V or 240 V, depending on the country. This voltage is too high to directly connect to the one or more diodes. Because the new LED lighting cannot be connected directly to AC power, one or more transformers or converters must be installed or included within the housing when implementing LED light sources.
In the current residential market, there are many options for LED replacement light bulbs, which fit into the standard Edison screw base socket, which supplies AC at mains voltage. Replacement LED bulbs incorporate a transformer or other power conversion circuitry in the housing of the bulb, typically within a cavity in the base of the bulb.
An LED replacement bulb, while vastly more efficient than an incandescent bulb it may be replacing, will generate significant heat. Both the diodes themselves, and the power converter generate waste heat, which is typically dissipated through a heatsink. In some designs, the exterior of the housing is used as a heat sink. Because of aesthetic considerations, large, efficient heatsinks are normally not used. The result is that the operating temperature of the bulb, is relatively high. While the diode junctions themselves are designed to be tolerant of high operating temperature, the circuitry providing DC voltage to the LED will experience extreme temperatures relative to its design. Heat-induced failure of the DC voltage supply is a common failure mode of such bulbs.
Typical LED replacement bulbs have a rated lifespan of 30,000-50,000 hours. However, the rating is based on the diode lifespan, rather than the bulb as a whole. Often, the DC power supply will fail long before the bulb reaches the rated lifespan.
Due to the limited space available within the bulb for electronics, it is not feasible to implement a larger, more robust power supply. Even if a larger power supply could be used, the issue of heat would still arise, due to the proximity of the (hot) LED units. For the bulb to fit within the base, and be aesthetically pleasing, the power supply must be internal.
Some LED lamps operate with an external power converter, which plugs into a standard AC receptacle and provides a better thermal environment for the electronics inside, by virtue of being external to the hot bulb. However, such “wall warts” and inline power adapters are bulky and unsightly, as well as often incompatible with each other due to the use of proprietary connectors.
Typical lamps supply voltage to the bulb mounts via simple wires connecting the terminals in the wall receptacle with the terminals in the mount, to supply the mains voltage to the socket. When plugged into a standard receptacle, the lamp supplies AC
Receptacles with ports for AC and low voltage DC are known, however these have the disadvantage of requiring a different connector than the standard AC mains plug.